1. Field of the Invention
The present invention is related to an auto-returning height-control assembly for a chair wherein a chair returns to its original place automatically when a person stands up from a chair or sits down on a chair and turns the chair.
2. Description of the Background Invention
FIG. 1 is a vertical cross sectional view which shows a conventional height adjusting assembly for a chair. The conventional height adjusting assembly comprises a outer cylinder 600, a spindle guide 500 which is inserted and fixed inside the outer cylinder 600 and a spindle 150 which slides along the inside surface of the spindle guide 500.
The spindle 150 is connected with a piston rod 110 and extends outwards toward the outer cylinder. The height of the spindle is adjustable along the axis of the piston rod and a push button (133), which is put on and off to make the spindle move up and down along the axis of the piston rod, is installed at an outer end of the spindle. An end of the piston rod 110 is fixed to the outer cylinder 600 with a fixing clip 235. An elastic member 620 for absorbing the shock which is put on the outer cylinder 600 by the lower end of the spindle 150 when spindle 150 moves up and down along the axis of the piston rod is inserted at the lower end of the piston rod 110. A thrust bearing 142 is inserted at the lower end of the shock absorbing cushion member 620. A movement preventing projection 135 is formed a the lower end of the piston rod 110 in order to prevent the thrust bearing 142 from moving upwards. As the shock absorbing cushion member 620 and the thrust bearing 142 are inserted at the piston rod 110, the shock put on the spindle 160 is absorbed and the rotation static-electricity is reduced. A push button 133 is formed at an outer end of the spindle 150 and the spindle is allowed to rotate and move up and down along the inside of the spindle guide 500 according to the operation of the push button in the conventional auto-returning height control assembly. In the conventional art, the push button used in adjusting the height of a chair is formed at an end of the spindle 150 and an operation lever 188 located at the lower end of the chair is used to push the push button 133 as shown in FIG. 2.
As the conventional auto-returning height control assembly is structured to control the rotation of the spindle 150 inside the spindle guide 500, the seat 121 of a chair does not return to its original place after a person has used the chair and made it rotate in a certain degree. In order to make the seat of a chair return to its place, an artificial force has to be put on and rotate the seat. Therefore, there is inconvenience in arranging seats of chairs into their original places after using them, and especially, when there are larger number of chairs, it is time and manpower consuming to do all the chairs.
The present invention is to overcome the problems of the convention art by providing an auto-return height control assembly in which the seat of a chair returns to its place automatically after using the chair.